Serine proteases are a large family of enzymes with diverse biological functions, their commonality being the presence and critical function of the active-site serine residue. Their central function is the catalytic scission of peptide bond substrates via a Ser, His, Asp triad within the active site (Kraut, J. Annual Review of Biochemistry 1977, 46, 331-358)
The present disclosure relates to compounds, e.g., pyrazolyl-substituted pyridone compounds, which exhibit biological activity, e.g., inhibitory action, against serine proteases, including thrombin and various kallikreins.
Kallikreins are a subgroup of serine proteases, divided into plasma kallikrein and tissue kallikreins. Plasma kallikrein (KLKB1) liberates kinins (bradykinin and kallidin) from the kininogens, peptides responsible for the regulation of blood pressure and activation of inflammation. In the contact activation pathway of the coagulation cascade, plasma kallikrein assists in the conversion of factor XII to factor XIIa (Keel, M.; Trentz, O. Injury 2005, 36, 691-709). Factor XIIa converts factor XI into factor XIa, which in turn activates factor IX, which with its co-factor factor VIIIa forms the tenase complex, which finally activates factor X to factor Xa. In the fibrinolysis part of the coagulation cascade, plasma kallikrein serves to convert plasminogen to plasmin. Thus, it has been proposed that plasma kallikrein inhibitors can be useful in the treatment of thrombotic and fibrinolytic diseases and disease conditions (U.S. Pat. No. 7,625,944; Bird et al. Thrombosis and Hemostasis 2012, 107, Dhaval Kolte, MD. et al., Cardiology in Review, 2015).
In rodent models, it has been shown that activation of plasma kallikrein in the eye increases retinal vascular permeability; whereas inhibition of the kallikrein-kinin system reduces retinal leakage induced by diabetes and hypertension. These findings suggest that intraocular activation of the plasma kallikrein pathway can contribute to excessive retinal vascular permeability that can lead to diabetic macular edema (DME). Thus, evidence suggests that plasma kallikrein inhibitors can provide a new therapeutic opportunity to reduce retinal vascular permeability (Feener, E. P. Curr Diab Rep 2010, 10, 270).
Hyperglycemic and diabetic individuals have an elevated risk of hemorrhage during thrombolytic therapy. In rodent models of intracerebral hemorrhage (ICH), it has been shown that KLKB1 inhibition or knockout reduces this effect. While the mechanism is not fully understood, this evidence suggests that plasma kallikrein inhibitors can be useful in the treatment of cerebral hemorrhage (Feener, E. P. Curr Diab Rep 2010, 10, 270).
Plasma kallikrein and Factor XIIa inhibitors have been shown to be neuroprotective in animal models of acute ischemic stroke and traumatic brain injury, reducing edema formation, inflammation, and thrombosis (Albert-Weiβenberger C, Siren A L, Kleinschnitz C. Prog Neurobiol. 2013, 101-102, 65-82.). Thus, evidence suggests that plasma kallikrein inhibitors can be useful in the treatment of acute ischemic stroke and traumatic brain injury.
Plasma kallikrein can also cleave glucagon-like peptide 1 (GLP-1) and neuropeptide Y (NPY), both substrates for dipeptidyl peptidase-4 (DPP-4), a validated diabetes drug target. In the case of GLP-1, cleavage by KLKB1 reduces both its potency as well as plasma stability. In the case of NPY, cleavage by KLKB1 reduces its affinity to the Y2 and Y5 receptors. Thus, evidence suggests that plasma kallikrein inhibitors can be useful in the modulation of energy homeostasis and in the treatment of diabetes. (Feener, E. P. Curr Diab Rep 2010, 10, Feener, E. P. et al., Biol. Chem. 2013, 394, 319).
The Kallikrein-kinin system is involved in the regulation of vascular endothelial growth factor (VEGF), endothelial NO synthase, and fibroblast growth factor 2, all of which are involved in angiogenesis (Bader M. 2009, Arteriosclerosis, Thrombosis, and Vascular Biology, 29: 617). Tissue kallikrein (KLK1) has been linked to blood vessel growth (Miura S., 2003, Hypertension, 41, 1118). Therapies that moderate angiogenesis have been proposed for the treatment of both diabetic macular edema (DME) and age-related macular degeneration (AMD) (Syed, B. A.; Evans, J. B.; Bielory, L., 2012, Nature Reviews Drug Discovery, 11, 827). Without further wishing to be bound by any theory, it is therefore reasonable to conclude that kallikrein inhibitors, including KLK1 inhibitors, can be useful in the treatment of diabetic retinopathy, DME, and AMD.
Studies have shown that inflammation plays an important role in the origin and development of AMD, and treatment often includes anti-inflammatories such as corticosteroid (Telander, D., 2011, Seminars in Ophthalmology, 26(3), 192). The connection between the kallikrein-kinin system and inflammation is also well established (Duchene, 2011, “Kallikrein-kinin kystem in inflammatory diseases”. Kinins. De Gruyter. 261). Without further wishing to be bound by any theory, it is reasonable to conclude that the anti-inflammatory nature of kallikrein (e.g. KLK1 and KLKB1) inhibitors can be useful in the treatment of AMD.
Ecallantide (Kalbitor) is a 60-amino acid recombinant protein that acts as a potent reversible inhibitor of plasma kallikrein (Schneider L, et al., J Allergy Clin Immunol 2007, 120, 416). Ecallantide has been approved by the FDA for the treatment of acute attacks of hereditary angioedema (HAE). Without further wishing to be bound by any theory, it is reasonable to believe that plasma kallikrein inhibition in general can be a useful treatment for HAE, and thus there is strong interest in the development of plasma kallikrein inhibitors as a therapy for HAE.
Tissue kallikreins (KLKs, for example, KLK1) are subdivided into various types, and have been extensively investigated in cancer and inflammation biology. Various kallikrein KLKs have been found to be up- or down-regulated in various cancer types, such as cervical-, testicular-, and non-small-cell lung adenocarcinoma (Caliendo et al. J. Med. Chem., 2012, 55, 6669). Furthermore, overexpression of various KLKs in the skin has led to the recognition that certain kallikrein inhibitors can be useful for certain dermatological conditions, including atopic dermatitis, psoriasis and rare skin diseases such as Netherton Syndrome (Freitas et al. Bioorganic & Medicinal Chemistry Letters 2012, 22, 6072-6075). A thorough discussion of tissue kallikreins, plasma kallikrein, their functions and potential roles in various diseases can be found in a variety of references, including the following which are incorporated herein by reference in their entireties and for all purposes: Renné, T.; Gruber, A. Thromb Haemost 2012, 107, 1012-3; Sotiropoulou, G.; Pampalakis, G. Trends in Pharmacological Sciences 2012, 33, 623-634; Pampalakis, G.; Sotiropoulou, G. Chapter 9 Pharmacological Targeting of Human Tissue Kallikrein-Related Peptidases. In Proteinases as Drug Targets, Dunn, B., Ed. The Royal Society of Chemistry: 2012; pp 199-228; Caliendo, G.; Santagada, V.; Perissutti, E.; Severino, B.; Fiorino, F.; Frecentese, F.; Juliano, L. J Med Chem 2012, 55, 6669-86.
Daiichi Seiyaku Co Ltd received approval in Japan to market cetraxate for gastritis and peptic ulcers. Cetraxate is reported as a plasma kallikrein inhibitor (WIPO Patent Application WO/2006/108643). Without further wishing to be bound by any theory, it is reasonable to believe that plasma kallikrein inhibition in general can be useful in the treatment of gastritis and peptic ulcers.
Thrombin (fIIa, the active form of prothrombin) is another serine protease that is involved in the coagulation cascade. In mammalian systems, blood vessel injuries result in bleeding events, which are dealt with by the blood coagulation cascade. The cascade includes the extrinsic and intrinsic pathways, involving the activation of at least 13 interconnected factors and a variety of co-factors and other regulatory proteins. Upon vascular injury, plasma factor VII interacts with exposed Tissue Factor (TF), and the resultant TF-fVIIa complex initiates a complex series of events. Factor Xa is produced directly ‘downstream’ from the TF-fVIIa complex, and amplified manifold via the intrinsic Pathway. FXa then serves as the catalyst for formation of thrombin (fIIa), which in turn is the direct precursor to fibrinolysis. The outcome is a fibrinolytic clot, which stops the bleeding. Fibrinolysis of the polymeric clot into fibrin monomers leads to dissolution and a return of the system to the pre-clot state. The cascade is a complex balance of factors and co-factors and is tightly regulated. In disease states, undesired up- or down-regulation of any factor leads to conditions such as bleeding or thrombosis.
Historically, anticoagulants have been used in patients at risk of suffering from thrombotic complications, such as angina, stroke and heart attack. Warfarin has enjoyed dominance as a first-in-line anticoagulant therapeutic. Developed in the 1940s, it is a Vitamin K antagonist and inhibits factors II, VII, IX and X, amongst others. It is administered orally, but its ease of use is tempered by other effects: it has a very long half-life (>2 days) and has serious drug-drug interactions. Importantly, since Vitamin K is a ubiquitous cofactor within the coagulation cascade, antagonism results in the simultaneous inhibition of many clotting factors and thus can lead to significant bleeding complications.
Much attention has been focused on heparin, the naturally-occurring polysaccharide that activates AT III, the endogenous inhibitor of many of the factors in the coagulation cascade. The need for parenteral administration for the heparin-derived therapeutics, and the inconvenient requirements for close supervision for the orally available warfarin, has resulted in a drive to discover and develop orally available drugs with wide therapeutic windows for safety and efficacy. Indeed, the position of thrombin in the coagulation cascade has made it a popular target for drug discovery. Without wishing to be bound by any theory, it is believed that the ultimate development of direct thrombin inhibitors (DTIs) is usefully based upon the classical D-Phe-Pro-Arg motif, a sequence that mimics fibrinogen, which is a natural substrate of thrombin. Without further wishing to be bound by any theory, it is believed that the use of DTIs is very well precedented, such as with the hirudin-based anticoagulants, and thus there is strong interest in the discovery and development of novel DTIs.
A thorough discussion of thrombin and its roles in the coagulation process can be found in a variety of references, including the following which are incorporated herein by reference in their entireties and for all purposes: Wieland, H. A., et al., 2003, Curr Opin Investig Drugs, 4:264-71; Gross, P. L. & Weitz, J. I., 2008, Arterioscler Thromb Vasc Biol, 28:380-6; Hirsh, J., et al., 2005, Blood, 105:453-63; Prezelj, A., et al., 2007, Curr Pharm Des, 13:287-312.
It will be obvious to one who is skilled in the art that plasma and tissue kallikreins and thrombin are only a few of the many serine proteases that are relevant to the treatment or prevention of certain disorders or diseases